ScubaMan2017
Headphoneus Supremus
Welcome to the thread, @Vindsvelle ! My 2 cents = if you want to mess around with different effects, I noticed the most dramatic results with my Vali 2. When I roll different tubes within it, my HD6xx (similar to your HD600) pick it up right away. I've had my new toy (Valhalla2 [stock SN2P & different flavours of SN1P paired tubes]). I can't detect the the differences. Your mileage may vary, however, you might have more luck with another model (if rolling + significantly different effects is your main goal). Meh, I'm happy with my toys.Greetings, everyone. I'm hoping you experienced Val users can provide some insight into my dilemma.
I'm currently in the 15 day audition period of the Valhalla with my HD 600, both bone stock, with ~50 hours cumulative load time on the Valhalla. I own a Sony STR-DG500 which, to my genuine astonishment, has proved to be an excellent SS headphone amp. Both it and the Val are fed by foobar2000 > WASAPI > cheap-o USB DAC > TOSLINK to the Sony / RCA (obviously) to the Val.
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Can I reasonably achieve the soundstage I want (up to and maybe beyond the soundstage the SS provides) with tube rolling? If so, with which tubes? I've heard mostly unanimous good things about the gold JJ 6922; I'd like to avoid tubes requiring adapters for the time being. Or am I barking up the wrong tree by trying to get an expansive soundstage with tubes at this pricerange?
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I have 9 days left in my trial period, and would greatly appreciate the feedback of all you experienced Val users, 6-series owners, and tube rollers to help me make an informed decision. Thanks.

BTW, would you consider upgrading your devices feeding your amplifier? Re: el cheapo DAC... that might benefit from an upgrade (Modi 3 or perhaps a Dragonfly?). Foobar's what I use and I particularly like its Win7 version (I use its Replay Gain mode). Re: your music files.... AAC? FLAC? ALAC? high-bit-rate-MP3?